1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device, wherein a touch panel is provided at a surface of a cover glass.
2. Discussion of the Related Art
Recently, as society becomes increasingly information dependent, a display field, wherein electrical information signals are visually displayed, has been developed rapidly. A variety of flat panel display devices having outstanding performances, such as a thin thickness, light weight and low electricity consumption, have been developed and have rapidly replaced conventional Cathode Ray Tubes (CRTs).
Examples of flat panel display devices include Liquid Crystal Display (LCD), Plasma Panel Display (PDP), Field Emission Display (FED), Electro-Luminescence Display (ELD) devices. These devices commonly include, as an essential constituent element, a flat display panel to form an image. The flat display panel is configured such that a pair of transparent insulating substrates is bonded to face each other with an illuminating or polarizing material layer interposed therebetween.
Of the above-mentioned display devices, LCD devices are designed to display an image by adjusting light transmissivity of liquid crystals using an electric field. LCD devices may include a display panel having liquid crystal cells, a backlight unit to irradiate light to the display panel, and drive circuits to drive the liquid crystal cells.
The display panel may be provided with a plurality of gate lines and a plurality of data lines, which cross each other to define a plurality of unit pixel regions. Each pixel region may include a thin-film transistor array substrate and color filter array substrate opposite each other, spacers located between the two substrates to maintain a cell gap, and liquid crystals filled in the cell gap.
The thin-film transistor array substrate may include the gate lines and data lines, thin-film transistors as switching devices formed at crossings of the gate lines and data lines, pixel electrodes arranged on a per liquid crystal cell basis and connected to the thin-film transistors, and an alignment film coated over all the above elements. The drive circuits may supply signals to the gate lines and data lines through respective pads.
The thin-film transistors may supply pixel voltage signals, supplied to the data lines in response to scan signals supplied to the gate lines, to the pixel electrodes.
The color filter array substrate may include color filters arranged on a per liquid crystal cell basis, a black matrix for division of the color filters and refraction of outside light, a common electrode commonly supplying a reference voltage to the liquid crystal cells, and an alignment film coated over all the above elements.
After the thin-film transistor substrate and color filter array substrate, which are fabricated separately, are aligned, the thin-film transistor substrate and color filter array substrate are bonded to face each other, and liquid crystals may be injected and sealed, to thereby complete the display panel.
Recently, demand for addition of a touch panels to LCD devices fabricated as described above is increasing. A touch panel senses a touch position of person's hand or other input means and transmits information in response to the sensed touch position. Currently, touch panels have been attached to an outer surface of the LCD device.
Hereinafter, a related art touch panel attached LCD device will be described with reference to the accompanying drawing.
FIG. 1 is a schematic view illustrating a touch panel attached LCD device.
As shown in FIG. 1, touch panel attached LCD device includes a liquid crystal panel 10 which includes first and second substrates 1 and 2, a liquid crystal layer 3 filled between the substrates 1 and 2 and first and second polarizers 4a and 4b attached to rear surfaces of the first and second substrates 1 and 2, respectively, a touch panel 20 which is placed on the liquid crystal panel 10 and is driven in a capacitive manner, and a cover glass 30 to protect the top of the touch panel 20.
Provided on the first substrate 1 of the liquid crystal panel 10 is a Thin-Film-Transistor (TFT) array including gate lines and data lines intersecting each other to define pixel regions, TFTs formed at intersections of the gate lines and data lines, and pixel electrodes in the respective pixel regions.
Provided on the second substrate 2 is a color filter array including a black matrix layer, a color filter layer and a common electrode.
The interior configuration of the touch panel 20 is changed according to a driving manner of the touch panel. For example, in the case of a capacitive touch panel designed to sense a touch position via a capacitance variation at a touch point, first and second electrodes intersecting each other are provided to enable sensing via a capacitance value variation between the electrodes.
To protect the touch panel 20, the cover glass 30 is provided on me top of the touch panel 20.
The above-described touch panel attached LCD device requires adhesive layers between the touch panel 20 and the liquid crystal panel 10 and between the touch panel 20 and the cover glass 30. In this case, the touch panel 20 and cover glass 30 are separately provided above the liquid crystal panel 10. There is a need for a processes for adhering the touch panel 20 and the liquid crystal panel 10 to each other and a process for adhering the cover glass 30 and the touch panel 20 to each other.
Now, problems of the above-described touch panel attached LCD device will be described.
The touch panel is provided as a sheath of the liquid crystal panel, together with the cover glass provided to protect the touch panel, and adhesive layers must be provided between the touch panel and the liquid crystal panel and between the cover glass and the touch panel. This inevitably entails additional attachment processes. Furthermore, since related art touch panels have at least two opposing substrates and two crossing electrodes, it takes many processes to make the related art touch panel attached LCD device. Further, if the touch panel and liquid crystal panel are misaligned, it is difficult to separate the touch panel attached to the liquid crystal panel because the cover glass is applied after attaching the touch panel to the liquid crystal panel, and forcible separation may damage the touch panel.